National Centre for Marine Conservation and Resource Sustainability, AMC Institute, University of Tasmania, Launceston, TAS, Australia.
J Appl Microbiol. 2013 Oct;115(4):923-32. doi: 10.1111/jam.12286. Epub 2013 Jul 19.
The Australian tuna industry is based on the ranching of wild southern bluefin tuna (SBT, Thunnus maccoyii). Within this industry, only opportunistic pathogens have been reported infecting external wounds of fish. This study aimed to identify different culturable bacteria present in three cohorts of SBT and to determine normal bacteria and potential pathogens in isolates from harvest fish and moribund/dead fish. Post-mortem changes in the microbiota were also studied.
Moribund/dead showed a greater proportion of members from the family Vibrionaceae than harvested fish; the latter presented mainly non-Vibrio species. In harvested fish spleens, Vibrio splendidus I complex was the most commonly identified group among Vibrio isolates, while most groups from the family Vibrionaceae were isolated from gills. For moribund/dead, Vibrio chagasii and Photobacterium damselae subsp. damselae were common in gill, spleen and kidney samples. Non-Vibrio isolates from gills were characterized using 16S rRNA sequencing as Flavobacteriaceae and classes Gammaproteobacteria and Alphaproteobacteria, mainly from the genera Winogradskyella and Tenacibaculum. Post-mortem changes showed dynamic shifts in bacterial dominance in gills, with Vibrionaceae and non-Vibrio spp. found in similar proportions initially and types related to Pseudoalteromonas ruthenica prevailing after 27 h. Spleen samples showed little bacterial growth until 5 h post-mortem, while various Vibrio-associated species were isolated 27 h post-mortem.
Bacterial isolates found include a range of potentially pathogenic bacteria that should be monitored though most of them have yet to be associated with disease in tuna.
This study forms a foundation for future research into the bacterial population dynamics under different culture conditions of SBT. An understanding of the bacterial compositions in SBT is necessary to evaluate the effects of some bacterial species on their health.
澳大利亚金枪鱼产业以养殖南方蓝鳍金枪鱼（SBT，Thunnus maccoyii）为主。在该产业中，仅报告了机会性病原体感染鱼类外部伤口。本研究旨在鉴定三种 SBT 群体中存在的不同可培养细菌，并确定来自收获鱼类和濒死/死亡鱼类的分离物中的正常细菌和潜在病原体。还研究了死后微生物群的变化。
濒死/死亡的鱼类比收获的鱼类有更多来自弧菌科的成员；后者主要为非弧菌类。在收获的鱼类脾脏中，Vibrio splendidus I 复合体是弧菌分离物中最常见的鉴定群体，而弧菌科的大多数群体都从鳃中分离出来。对于濒死/死亡的鱼类，Vibrio chagasii 和 Photobacterium damselae subsp. damselae 在鳃、脾和肾组织样本中很常见。从鳃中分离出的非弧菌类通过 16S rRNA 测序鉴定为黄杆菌科和γ变形菌纲和α变形菌纲，主要来自 Winogradskyella 和 Tenacibaculum 属。死后变化显示了鳃中细菌优势的动态变化，最初发现弧菌类和非弧菌类的比例相似，而与 Pseudoalteromonas ruthenica 相关的类型在 27 小时后占主导地位。脾脏样本在死后 5 小时内几乎没有细菌生长，而在 27 小时后分离出各种与弧菌相关的物种。
发现的细菌分离物包括一系列潜在的致病性细菌，尽管其中大多数尚未与金枪鱼疾病相关联，但仍应进行监测。
本研究为未来研究 SBT 不同养殖条件下的细菌种群动态奠定了基础。了解 SBT 中的细菌组成对于评估某些细菌物种对其健康的影响是必要的。
